Rubidium-strontium geochronology and plate-tectonic evolution of the southern part of the Arabian Shield

____________________________________ Introduction __________________________ Acknowledgments ____________________ General geologic setting ___________________________ Volcanic and sedimentary rocks ___________ Basaltic assemblage ______________ Andesitic assemblage ________________ Plutonic rocks _____________________________ Dioritic batholiths ________________ Granodiorite gneiss ___________ Late-orogenic or postorogenic plutons _______ Layered gabbro and associated rocks __ Granodiorite to granite intrusions ____ Najd fault system ______________________ Previous geochronologic studies ____________________ Analytical techniques _____________________ Results of rubidium-strontium analyses __________ Basaltic assemblage _________________________ Page